family study of pediatric patients with primary antibody deficiencies.

common variable immunodeficiency (cvid) and selective iga deficiency (sigad) are the most common primary antibody deficiencies. these two diseases may have coincidence in one family and sigad can progress to cvid which suggest common underlying genetic defects between sigad and cvid. this study was designed to find the prevalence of multiple cases in families of iranian patients with cvid or sigad. serum samples were collected from all available first-degree relatives of 37 patients (23 patients with cvid and 14 with sigad) to check the levels of immunoglobulin and their subclasses and detect antibody deficiencies. first degree family members of 37 patients (106 individuals) were enrolled in this study. thirty two percent of patients had multiple cases in their families. the frequency of primary antibody deficiency in the first relatives of the patients was estimated to be one per 9 family members. most of the patients found among family members were siblings of the primary patients. analysis in sigad family members showed that igg and iga levels in families with multiple cases were significantly lower than family members without multiple cases (p values of 0.048 and 0.021, respectively). rate of families with multiple cases in iran is more than the previous studies in other countries. this rate was not affected by the consanguinity of parents (p=0.081) or immunoglobulin level of the patients. because of higher risk for the prevalence of these disorders in those with a positive family history of immunodeficiency, family screening programs in the patients with cvid and sigad can be suggested to be prioritized..